A typical liquid crystal display (LCD) is capable of displaying a clear and sharp image through thousands or even millions of pixels that make up the complete image. The liquid crystal display has thus been applied to various electronic equipment in which messages or pictures need to be displayed, such as mobile phones and notebook computers. A liquid crystal panel is a major component of the LCD. The liquid crystal panel generally includes a thin film transistor (TFT) array substrate, a color filter substrate opposite to the TFT array substrate, and a liquid crystal layer sandwiched between the two substrates.
Referring to FIG. 16, part of a typical TFT array substrate is shown. The TFT array substrate 100 includes a plurality of parallel gate lines 110, and a plurality of parallel data lines 120 perpendicular to the plurality of gate lines 110. The plurality of gate lines 110 and data lines 120 cross each other to define a plurality of pixel units. Each pixel unit has a thin film transistor (TFT) 130, a pixel electrode 140, and a storage capacitance electrode line 150. The TFT 130 is disposed at an intersection of a corresponding one of the gate lines 110 and a corresponding one of the data lines 120. The TFT 130 has a gate electrode 131 connected to the gate line 110, a source electrode 132 connected to the data line 120, and a drain electrode 133 connected to the pixel electrode 140. The storage capacitance electrode line 150 is parallel to the gate lines 110, and forms a storage capacitance with the pixel electrode 140.
Referring also to FIG. 17, the TFT array substrate 100 further includes: a substrate 101, the gate lines 110 and the storage capacitance electrode line 150 being formed on the substrate 101; a gate insulating layer 102 formed on the substrate 101 having the gate lines 110 and the storage capacitance electrode line 150; a semiconductor layer 103 formed on the gate insulating layer 102, the source electrode 132 and the drain electrode 133 being formed on the gate insulating layer 102 and the semiconductor layer 103; and a passivation layer 104 formed on the gate insulating layer 102, the source electrode 132 and the drain electrode 133. The pixel electrode 140 is formed on the passivation layer 104, and electrically connects with the drain electrode 133 through a through hole 105 defined in the passivation layer 104.
The pixel electrode 140 is made from Indium Tin Oxide (ITO). The gate lines 110 electrically connect with an external driving circuit. The gate lines 110 and the storage electrode lines 150 are made from molybdenum (Mo), which can help avoid chemical reaction occurring between the gate lines 110 and the storage electrode lines 150.
A method of manufacturing the TFT substrate 100 includes the following steps (described in relation to a part of the TFT array substrate 100 only): forming a gate metal layer; forming a gate electrode; forming a gate insulating layer and an amorphous silicon (a-Si) and doped a-Si layer; forming a semiconductor layer on the gate insulating layer; forming a source/drain metal layer; forming source/drain electrodes; forming a passivation material layer; forming a passivation layer; forming a transparent conductive layer; and forming a pixel electrode. However, the method includes five photo-mask processes, each of which is rather complicated and costly. Thus, the method for fabricating the TFT array substrate 100 is correspondingly complicated and costly.
What is needed, therefore, is a method for fabricating a TFT array substrate that can overcome the above-described problems.